To prepare the achari karela first of all you need to prepare bitter karela to remove the bitterness.
Wash and peel the karela, if you want you can keep the peel and make a stir fry of that too later ( I will be posting the recipe of that too)
After peeling the karela, cut them in half, if you feel seeds are too ripe and hard just discard them. Now put about a teaspoon of salt over it and keep it in sun for 1-2 hours.
After that just wash the karela and pat dry with kitchen napkin before proceeding to cook the achari karela aloo.
Peel the potatoes and cut them into thick roundels.
If you still feel that karela is too bitter, after salting them you can place them in boiling water which will further reduce the bitterness of the karela.
Now heat up the mustard oil in a kadahi or wok and add all the seeds, let the seeds start to sizzle, and then add cut potato in the wok, also add cut bitter melon/ karela.
Cover and cook them for next 6-7 minutes on medium slow heat. Now remove the lid and lower the heat to slow and let the bittermelons and potato become crisp from all sides.
Finally add chopped tomato, chopped mango pickle (if you are using) and cook everything for 4-5 minutes on medium heat. Stir it in between.
Achari karela will be ready then. It tastes best with chapati or paratha.